The present invention relates to a motor-driven compressor.
Japanese Laid-Open Patent Publication No. 2003-120555 discloses an example of a motor-driven compressor that includes a compression unit, which includes a fixed scroll and a movable scroll capable of orbiting the fixed scroll, and an electric motor, which includes a rotor and causes the movable scroll to orbit. The motor-driven compressor includes a compression chamber that is defined by the fixed scroll and the movable scroll and draws in an intake fluid. The orbiting of the movable scroll compresses the intake fluid in the compression chamber and discharges the compressed fluid.
Japanese Laid-Open Patent Publication No. 2003-120555 also describes a motor-driven compressor that includes an injection port, which draws an intermediate pressure fluid having higher pressure than the intake fluid into the compression chamber, and an air conditioner including the motor-driven compressor. The air conditioner includes, for example, an injection pipe connected to the injection port and a gas-liquid separator connected to the injection pipe. The intermediate pressure fluid flows out of the gas-liquid separator and into the compression chamber through the injection pipe and the injection port. This increases the flow rate of the fluid flowing into the compression chamber.
When the motor-driven compressor, which is configured to draw the intermediate pressure fluid into the compression chamber as described above, is deactivated, the residual intermediate pressure liquid in the injection pipe may flow into the compression chamber through the injection port. This may result in a reverse rotation action in which the movable scroll orbits in a direction opposite to the forward direction and reverses the rotation of the rotor. In this situation, noise and vibration tend to increase when the rotational frequency (rotation speed) of the rotor is high.
To promptly stop the rotor, the electric motor may undergo, for example, a forcible deactivation control that forcibly stops the reverse rotation of the rotor. In this case, the intermediate pressure fluid may continue to remain in the injection pipe. The intermediate pressure fluid may cause a reverse rotation recurrence action in which after the rotation of the rotor is stopped, the rotor reversely rotates again. The reverse rotation recurrence action may interfere with, for example, the activation of the motor-driven compressor.